The present invention relates to thermoplastic bags useful for packing groceries, and, in particular, to a method of providing a convenient structure for opening such bags, one bag at a time, from a bag pack which includes a supply of bags hung together at a bag dispensing station.
In the past, it has been known to manufacture bags having different configurations in order to provide convenient means of packaging for various uses. For example, it has been known to provide a thermoplastic bag with loop handles which are integral with the bag and can be easily formed by cutting a T-shirt-like formation in a stack of bags. The integral handle can be reinforced by providing a double overlap on either edge of a thermoplastic tube such as by gussetting the tube over folding elements provided in the manufacturing line.
For example, U.S. Pat. No. 4,597,749 to O'Brien, et al. discloses a thermoplastic bag characterized by having a pair of carrying handles formed integrally with the bag walls and extending upwardly from the opposite sides of an open mouth portion of the bag. The handle members are reinforced and comprise at least two layers of thermoplastic material, one of the layers forming the bag, body and handles and the other layer serving as a reinforcement layer, the reinforcement layers being provided only in the handle areas of the bag structure.
In U.S. Pat. No. 4,588,392 to Maddock a plastic film sack having gussetted sidewalls is disclosed wherein a heat-seal stripe welding is provided in the bottom of the sack to gather four film layers in the gussetted regions of the sack while a heat-seal stripe welding gathers the two film layers between the gussetted regions. Between the heat seal stripes of the four film layers and the heat-seal stripe of the two film layers are unsealed arcuate stress relief regions.
In U.S. Pat. No. 4,554,192 to Benoit a bag structure for thermoplastic material is disclosed wherein there are front and rear bag walls connected by sidewalls which has an open mouth top portion. The open mouth portion is characterized by having handles located at opposite end regions, such handles having two films as a result of being integral extensions of the front and rear gussetted sidewalls. The bag also has a bottom wall planarly extensible so as to form a rectangle with at least no substantial excess film outside of the bulk volumetric capacity of the bottom region of the bag.
In U.S. Pat. No. 4,493,419 to Prader, et al. a bag pack of a plurality of stacked thermoplastic bag structures is disclosed wherein each bag has a front and rear bag wall and an open mouth top portion. Handles are integral extensions of the bag walls. The bags are bonded together via bonding means in association with the handles. Individual bags may have stress release curves in the handles and the bag mouth opening.
U.S. Pat. No. 4,476,979 to Reimann, et al. discloses a bag pack and individual bags characterized by having handles which are integral extensions of the front and rear of the bags. The bags have a bag mouth which includes stress release curves on both sides of an upwardly extending tab. The tab includes at least one opening which is positioned to create comparatively narrow webs which serve to be tear-off points severing individual bags from the pack. The bags are bonded together via the tab at areas adjacent the openings.
See also U.S. Pat. No. 4,464,157 to Benoit, et al. which relates to thermoplastic bag structures characterized by having a pair of carrying handles formed integrally in the bag walls and extending upwardly from opposite sides of the open mouth portion of the bag. The handle bags are particularly characterized in having reinforced handle members having two layers of thermoplastic material, one of the layers imparting tensile strength to the individual layer and the other layer particularly employed to provide requisite puncture and tear resistance necessary in such a bag structure.
In U.S. Pat. No. 4,604,084 to Pistner a thermoplastic bag structure is disclosed which has a front and rear bag wall, a bottom and an open mouth top portion, the open mouth portion having two pairs of single film handle loops each of which are located at opposite ends of the open mouth portion. The bag structures are unitized by providing a detachable tab at the mouth opening and unitizing the bag structures through this tab. The method of forming the bags involves providing an end seal collapsed thermoplastic film tube and removing plastic to form a bag mouth opening and handles at one end thereof. The resulting bag is an ungussetted bag which can be unitized into a pack by providing a detachable, unitizing tab at the bag mouth opening.
In some of the most recent developments in the area of providing thermoplastic bags at grocery counters, it is necessary to provide an opening through the pack of bags for mounting on a tab which is located on a rack generally located at the end of the grocery counter. The bags such as those shown in the Reimann, et al. '979 patent must then be unthreaded one side at a time over the mounting tab and expanded over arms in order to form a wide mouth opening for packing the plastic bags. This method generally suffers from the drawback that the front and back sides of each of the bags are bonded or welded together such as by means of heat sealing or otherwise. In the Reimann, et al. '979 patent, the bags are bonded together on a tab adjacent the opening. This feature reduces the ability of the packer to separate the sides of the bag to form the open mouth receptacle.
Thus, it is a primary object of the present invention to provide a method for forming a thermoplastic bag having an easily separable bag mouth opening by providing one side of the bag relatively free for opening from the other side of the bag.